docs: def addDelta(self, location, aMathObject, deltaName = None, punch=False,  axisOnly=True):
          """ Add a delta at this location.
              *   location:   a Location object
              *   mathObject: a math-sensitive object
              *   deltaName: optional string/token
              *   punch:
                  *   True: add the difference with the instance value at that location and the delta
                  *   False: just add the delta.
          """
          #location = self._bender(location)
          if punch:
              r = self.getInstance(location, axisOnly=axisOnly)
              if r is not None:
                  self[location.asTuple()] = aMathObject-r, deltaName
              else:
                  raise MutatorError("Could not get instance.")
          else:
              self[location.asTuple()] = aMathObject, deltaName